Nf. Butte et al., CHANGES IN FAT-FREE MASS AND FAT MASS IN POSTPARTUM WOMEN - A COMPARISON OF BODY-COMPOSITION MODELS, International journal of obesity, 21(10), 1997, pp. 874-880
OBJECTIVES: (1) To compare 2-, 3- and 4-component models of body compo
sition based on total body water (TBW), underwater weighing (UWW), ski
nfold thicknesses (SF), total body potassium (TBK), dual-energy X-ay a
bsorptiometry (DXA) and total body electrical conductivity (TOBEC); (2
) to compare postpartum changes in body composition estimated by the 2
-, 3- and 4-component models and (3) to test for an effect of pregnanc
y or lactation on the hydration, density and potassium content of fat
free mass (FFM) in postpartum women. DESIGN: Longitudinal measurements
of body composition at 3, 6 and 12 months postpartum. SUBJECTS: Thirt
y-five healthy postpartum women, aged 30.2+/-3.5 y. MEASUREMENTS: Body
composition was estimated by 2-component models based on TBW, UWW, SF
, TBK, DXA or TOBEC; 3-component models based on TBW and UWW (Fuller 3
, Siri 3); and a 4-component model (Fuller 4) based on TBW, UWW and bo
ne mineral content. RESULTS: Systematic differences were seen among th
e various body composition models, with the following ranking from low
est to highest estimate of fat mass (FM): TOBEC, TBW, Fuller 3, Siri 3
, Fuller 4, UWW, SF, TBK, and DXA. Estimated changes in FFM and FM wer
e not significantly different among methods, except for the 3-6 months
FFM and FM changes estimated from TBW, which differed from SF, DXA, a
nd TOBEC. Pregnancy-induced changes in the hydration, density and pota
ssium content of FFM were not evident by 3 months postpartum (0.73+/-0
.02, 1.099+/-0.015 kg/l and 2.31+/-0.10 g/kg, respectively). CONCLUSIO
N: In spite of systematic differences among body composition models fo
r the measurement of FFM and FM, changes in FFM and FM did not differ
significantly among the models. Since there was no apparent effect of
pregnancy or lactation on the postpartum composition of FFM, 2-compone
nt models of body composition are acceptable for mse in postpartum wom
en beyond the puerperium.